The leftist party exploded out of Spain’s anti-austerity protests in 2011 and upended Spain’s entrenched two-party system. I was instantly captivated – and for the next decade, I worked for the party. But I ended up quitting politics in disappointment. What happened? This article originally appeared in Equator, a new magazine of politics, culture and art I never expected to retire in my 30s, but I suppose politics is the art of the impossible: what it promises, what it extracts. A decade at the heart of Spain’s boldest modern political experiment aged me in ways I’ve only just begun…